Ion-pairing reagents are not compatible with preparative chromatography, LC/MS, and ELS detection.
Primesep® columns offer an alternative way to retain polar compounds through ion-exchange mechanism with embedded ion-pairing groups. The amount of ion-pairing groups on Primesep columns is comparable to the amount of ion-baring groups on regular ion-exchange columns.
In many instances, reverse phase columns designed for retention of polar compounds do not offer enough capacity when a sample for separation has a high ion-strength. Primesep® columns have a high capacity for ion-exchange mechanism. It is especially important for preparative chromatography. Sample loading on the column is one of the most important characteristic of the stationary phase when used in scale up separations. This characteristic is demonstrated by Primesep® 100 in separation of polar compounds as shown on the graph on the left.
High loading capacity observed for polar compounds on Primesep 100 column, which is important for preparative separation.
Isocratic method can be developed for separation of compounds with drastically different polarity. Primesep® columns are ideally suited for universal detectors such as ELSD and MS.
Often, compounds without chromophores have low hydrophobicity and retain poorly on reverse-phase columns. Ion-exchange columns show low selectivity to compounds with similar pKa value. In traditional ion-exchange chromatography non-volatile buffers are used. This greatly complicates application of ion-exchange chromatography with evaporative detectors such as MS and ELSD.
This example demonstrates the separation of amino acids on a Primesep 100 column by reverse-phase and ion-exchange mechanism.